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How does Vehicle to Grid (V2G) technology work?

Tags: #vehicle-to-grid-v2g

Vehicle to Grid (V2G) charging is considered one of the next big evolutions in the way we manage not only how we use EVs, but how we use energy in general. Effectively a two-way interface between the power grid and an EV's battery, it's a massive step towards smart energy management which will allow us to use less energy, as well as reducing carbon emissions.

What is V2G?

Essentially it is what the name suggests – a means by which an electric vehicle is linked to the electricity grid.

Traditionally, the flow of power was one directional, from centrally-generated sources and flowing into the battery of a plugged-in EV. Like any other appliance or gadget that requires charging, EVs simply draw power until they are fully juiced at which point on-board charging management halts the intake of power automatically. The car's battery then stores the energy it has drawn to be used exclusively in powering it.

V2G enables bidirectional power flow. EVs can both draw power from the grid to charge and discharge it back into the grid when it is required. This could be when overall power demand from the grid is high, or when renewables such as solar or wind aren't generating as much power as usual due to weather conditions.

Why do we need V2G?

At the moment the supply and demand of power into and from the grid is managed on a large-scale basis. The amount of power required is fed in from power stations, wind farms, solar, and so on, and the National Grid can 'turn up the gas' when power demand increases, or turn it down when it decreases. These peaks and troughs are broadly known, but currently dealing with them is done with very broad, rather than finessed, mitigation measures which are far less efficient than they could be. This has significant costs in terms of wasted energy and emissions.

The need for V2G technology is several-fold. Firstly, as the number of EVs on the roads increases, thus the demand on the grid will increase. Studies have shown that the grid can keep up with demand, but that's not to say it'll be efficient in doing so in its current form. And the fact is that as much as EVs are potentially creating a problem, they can also be central to solving it.

V2G technology means that stored energy in a plugged-in EV’s battery can be drawn back into the grid when it's required and replenished when the grid has less demand placed upon it. Drawing power from an EV might be required when green generation is low because it’s not a particularly windy of sunny day for wind turbines or solar panels to prove effective. It could also smooth out the evening peak when people get home and plug their cars and phones in, and turn the kettle on. Power can then be put back into EVs when demand is lower – such as overnight.

V2G helps smooth out the peaks and troughs in demand and supply without the grid having to increase centralised, carbon-intense generation. It will also form a central element in the move towards smart grid technology, where energy management can be done on a much localised scale for maximum efficiency.

Is V2G already operating in the UK?

In a word, yes. But to add detail to that, despite it being trialled as far back as 2015 in the UK, it's still only happening on a very limited scale.

The world's largest V2G trial site is based in London around TfL's fleet of electric buses – the largest such fleet anywhere in the world. The Bus2Grid project utilises the power stored in the batteries of up to 28 electric buses when they are plugged in at the depot in the north of the city. They can return more than 1 megawatt to the grid if required – helping to stabilise it.

At the moment the scheme is comparatively small-scale and has been funded by the government in conjunction with various bodies including Leeds University, UK Power Networks, TfL, bus operator Go-Ahead London and the bus manufacturer, Chinese firm BYD. SSE Enterprise, which is managing the hardware side of things, reckons that if London's entire bus fleet was converted to electric, the V2G aspect could balance power for up to 150,000 homes.

Trial schemes for individuals to benefit from V2G charging are also taking place around the UK. Orkney has been operating a small-scale trial scheme since early 2019. Called ReFLEX, it is based around micro generation (10 per cent of homes there generate their own electricity) and use EVs as 'power sumps' to balance the grid when required.

Electric Nation – a project by Western Power Distribution – has recently recruited 100 V2G-capable Nissan EV owners to take part in a V2G trial to test how it can work for individuals. Unlike many other such trials, five different electricity suppliers are taking part which should offer a better spread of data. Mike Potter, CEO of CrowdCharge (a part of Electric Nation), said: “Vehicle to grid charging is a great concept, but it hasn’t yet been trialled sufficiently on Britain’s electricity networks to enable it to be rolled out on a country-wide basis – hence the need for this project. This trial will study the real-world effects of V2G and look to provide a smart solution to provide management of electric vehicle charging.”

Speaking of Nissan, it has been at the forefront of V2G development (in part because its EVs are built with the CHAdeMO charging technology required – more below) working with energy suppliers such as EDF in Europe and most recently E.ON here in the UK. In partnership with E.ON, Nissan GB has installed 20 V2G chargers at its European Technical Centre in Cranfield. It's looking to roll-out the scheme more widely, too.

Finally, Octopus Energy has already jumped ahead of the game in offering a complete V2G bundle – Nissan LEAF and all – to customers here in the UK. Launched last August, Octopus was offering customers a Wallbox V2G charger and new 40kWh Nissan LEAF for a ludicrously reasonable £299 per month. The bargain was that customers were to leave their cars plugged in between 6pm and 5am at least 12 times per month. During that overnight time, Ocotpus could draw energy from customers' cars, but in return the customers got £30 cashback.

Why isn't V2G already more common?

Whilst the technology to support widespread V2G already exists, it's not blanketed across all EVs and all energy suppliers. The most fundamental limitation to the wide deployment of it is in the type of charging connection that EVs have.

At present, V2G charging is only possible with CHAdeMO charging technology. Its development is fundamentally based around two-way energy flow capability and its members work to defined specifications, testing criteria and certification on both the EV and charger side. It also has backward compatibility so current systems will be compatible with any developments made in future. The latest version of CHAdeMO charging can operate at DC speeds of up to 500kW, so it's definitely future-ready.

Here in the UK, Nissan is the only manufacturer that offers CHAdeMO charging on its EVs.

The Combined Charging System (CCS), which is far more widely used, isn't currently capable of bidirectional charging. However, plans are afoot to develop it so that vehicle to home (V2H) and then V2G charging will be supported by 2025. There's no guarantee – and in fact it's unlikely – that current cars using CCS will be V2G-enabled down the line.

As you can see, CCS becoming bidirectional charging-capable is a stumbling block for the widespread roll-out of an effective V2G network both here, and in other markets.

What does the future hold for V2G?

The National Grid Electricity System Operator's Future Energy Scenarios report, released in July, reckons that up to 45 per cent of UK households will provide V2G services by 2050. This could deliver up to 38GW of energy flexibility from an assumed 5.5 million EVs – though this is a best-case scenario. In the worst-case scenario, just 10 per cent of this capability would be reached.

Another factor to bear in mind is that the roll-out of V2G will likely be slow initially, with adoption by individuals lagging behind them switching from internal combustion to EV. The report suggests this lag could be anything from five to 15 years. That initial sluggishness is also predominantly down to the required development of CCS before it supports bidirectional charging.

Marcus Stewart, Principal Advisor, National Grid ESO, comments: “The CCS pathway is understood and we don’t see too much V2G in the early part of the scenarios. In 2050, take-up ranges from 5 to 45 per cent across the scenarios, with 45 per cent being the ‘Leading the Way’ early delivery of Net Zero. The two other Net Zero compliant scenarios assume 11 per cent and 26 per cent in 2050. This reflects the uncertainty around the take up of V2G.”

On the vehicle manufacturer side of things, Nissan is very much the leader in V2G but others are exploring it – though notably, the forthcoming Nissan Ariya will be CCS-only and not V2G-capable. BMW is developing its bidirectional charging technology and should have trials starting in early 2021 and running for a year. The company is calling for other stakeholders – including charging hardware and management, communication interfaces and energy suppliers – to also pull their weight.

Audi recently announced that it too is researching bidirectional charging as part of its goal to make its vehicle fleet carbon neutral by 2050. Audi's research is more about vehicle to home (V2H) than V2G, however, and is focussing on those people who have equipped their houses with solar panels (photovoltaic – or PV – systems). In this case, the car would act as a decentralised storage medium for energy into which PV-generated energy could be fed when it is operating most efficiently. When PV isn't as effective, the energy could then be drawn from the car to make up the shortfall. A pre-set state of charge would be maintained in the car to ensure that it's always ready to go if needed.

Audi reckons that its current e-tron could power a typical home for as long as a week, and as a separate inverter isn't required, it is a highly cost-effective solution.

Finally, Tesla is a bit of a V2G enigma in that is has been hesitant to openly embrace the idea due to the potential degradation to its batteries and also the comparatively small size of its vehicle fleet. However, V2G capability has been confirmed to have been built into the Model 3's electronic architecture – discovered by another carmaker which performed a tear-down of a Model 3, rather than officially confirmed by Tesla itself. It has been widely reported that the inverter within the Model 3 is fully capable of not only turning AC input to DC, but also feeding it from the DC battery back onto the AC side.

A limitation to Tesla becoming properly V2G-capable is the fact it uses CCS2 connection which, as noted above, is yet to be bidirectional. What we do know about Tesla is that it's regularly ahead of the game, so with schemes like Powerwall, Autobidder, and its recent application to become an energy supplier here in the UK, it's not too much of a stretch to think that the company is looking five years ahead of where we are now.

Conclusion

Vehicle to Grid technology is definitely going to be a big part of how we manage energy in the future. Whilst it is available already, the limitations of needing to have the right car – i.e. a Nissan – and the requisite hardware mean it's only a viable option for a minority of EV owners. Be in no doubt that over the next five years it will gain traction, and as soon as CCS is bidirectional-capable the technology is going to sky-rocket in popularity.

In many different areas of EV development and wider legislation that affects our transport choices, 2025 is looking to be a sweet spot. Our estimation is that after a slow gestation in the next few years, it is then that V2G will become mainstream.



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